1. Field of the Invention
The present invention relates to a disk drive which drives to rotate a disk such as a CD and a DVD which are used as recording media.
2. Description of the Related Art
In recent years, when reading data from and writing data onto disks such as CDs and DVDs which are used as recording media, a method is generally used in which a pickup or read/write head is caused to glide in a radial direction while rotating a disk. As this occurs, a disk drive such as shown in (JP-A-2003-348812) is used as a device for driving to rotate the disk.
Hereinafter, a conventional disk drive will be described using FIG. 15.
FIG. 15 is a sectional view of a main part of a conventional disk drive.
In FIG. 15, reference numeral 100 denotes a conventional disk drive, 101 a base portion, 102 a cylindrical bearing holding portion provided substantially at a central portion on an upper surface of the base portion, 103 a bearing portion held in an inside of the bearing holding portion 102, 104 a thrust plate fittingly fixed in a lower opening of the bearing holding portion 102, 104a a thrust bearing sheet, 105 a stator, which will be described later on, made up of a stator core and coils and provided in such a manner as to surround circumferentially the bearing holding portion 102, 105a a stator core, 105b a coil wound around each of tees of the stator core 105a, 106 a circuit board affixed to the upper surface of the base portion 101, 107 a Hall element electrically connected and fixed to an upper surface of the circuit board 106, 108 a spindle rotatably supported on the bearing portion 103, 109 a turntable fixed to the spindle, 109a an annular yoke made to suspend vertically from an outer circumferential portion of the turntable 109, 110 an annular magnet provided on an inner side of the yoke portion 109a in such a manner as to oppositely face distal end portions of the tees of the stator core 105a, 111 a slip preventive material affixed near an outer circumferential portion of an upper surface of the turntable 109, 112 a disk holding portion provided at a central portion of the upper surface of the turntable 109 to hold a disk placed on the turntable 109, 113 a disk holding claw provided in such a manner as to move into and out of a sliding groove portion formed in such a manner as to extend from an outer circumferential portion of the disk holding portion 112 towards a central portion thereof, 114 a spring provided in an inside of the sliding groove portion so as to bias the disk holding claw 113 in such a manner as to protrude from the outer circumferential portion of the disk holding portion 112, 115 a hook locking portion formed an outer circumferential portion of an upper end portion of the bearing holding portion 102, and 116 a hook portion provided at a predetermined portion on a lower surface of the turntable 109 in such a manner as to be brought into engagement with the hook locking portion 115.
In the conventional disk drive 100 that is configured as has been described above, a plurality of hook portions 116, which are formed by curving a metallic material, are provided around a circumference of the spindle 108, and the hook portions 116 are brought into engagement with the hook locking portion 115 on of the bearing holding portion 102 in such a state that the spindle 108 is securely inserted into the bearing portion 103, whereby the floating of the turntable 109 in association with the removal of an installed disk is prevented to thereby prevent the dislodgement of the spindle 108 from the bearing portion 103.
In addition, the base portion 101 is formed by being punched from a relatively thick sheet metal so as to be imparted a predetermined mechanical strength because a load is exerted thereon when a disk is installed and removed.
The stator core 105a is fixed to the bearing holding portion 102 at an inner circumferential portion thereof and is provided above the base portion 101 at a predetermined interval.
In addition, an annular magnet 117 is adhesion fixed to an upper surface of the inner circumferential portion of the stator core 105a, so that the floating of the turntable 109 while rotating is prevented by virtue of a magnetic attraction force which attracts a lower surface of the turntable 109.
In addition, the base portion 101 and the thrust plate 104 are strongly fixed to the bearing holding portion 102 by plastically deforming annular portions 102a, 102b which are provided on a lower surfaces of the bearing portion 102 through pressing.
Additionally, a predetermined gap 118 is imparted between a lower portion of the disk holding claw 113 and the upper surface of the turntable 109.
Next, a state will be described in which a disk is installed using FIGS. 16(a) to (d) which are sectional views of a main part of the conventional disk drive 100 showing a process of installation of a disk D.
Here, FIG. 16(a) is a sectional view of a main part of the conventional disk drive which shows a state resulting before the installation of the disk D, FIG. 16(b) is a sectional view of the main part of the conventional disk drive which shows a state resulting at an initial stage of the installation of the disk D, FIG. 16(c) is a sectional view of the main part of the conventional disk drive which shows a state resulting at a middle stage of the installation of the disk D, and FIG. 16(d) is a sectional view of the main part of the conventional disk drive which shows a state resulting after the installation of the disk D, with the spring 114 omitted for the purpose of easing the understanding of the process.
Firstly, as shown in FIG. 16(a), a gradient surface 113d which is inclined towards a radially outside of an upper surface portion 113c and a radially outside distal end portion 113b are formed on the disk holding claw 113.
On the other hand, a sliding surface 112a which is inclined radially inwardly is provided on the disk holding portion 112 at a position which oppositely faces a distal end lower surface 113a of the disk holding claw 113.
Next, as shown in FIG. 16(b), the disk holding claw 113 slides in a radially inward direction indicated by an arrow along the sliding surface 112a. 
Furthermore, as shown in FIG. 16(c), a sliding amount of the disk holding claw 113 becomes maximum in such a state that an inner circumferential wall of a center hole of the disk D coincides with the distal end portion 113b of the disk holding claw 113.
Then, as shown in FIG. 16(d), while the disk D is brought into engagement at the center hole thereof when the disk is brought into abutment with an upper surface of the slip preventive material 111 and the disk holding claw 113 is biased by the spring 114 (not shown) so as to protrude, since the gap 118 is imparted, the disk holding claw 113 tilts about a fulcrum 112b, and therefore, there is produced a state in which the upper surface 113c of the disk holding claw 113 protrudes further upwards than an upper surface 112c of the disk holding portion 112.
The gradient surface 113d which is inclined radially outwardly is provided on an upper surface on a radially outside of the disk holding claw 113 with a view to reducing a protruding amount which is a vertical distance between the upper surface 113c of the disk holding claw 113 and the upper surface 112 of the disk holding portion 112 as one of the purposes of the provision thereof.
On the other hand, a spindle motor, in which a plurality of window portions are opened along a circumferential direction of a base plate at predetermined intervals, is disclosed in (P JP-A-5-38115) as a conventional spindle motor that is used as a drive portion of the conventional disk drive.
According to Patent Document No. 2, an axial length can be reduced by allowing part of each winding portion of a stator to enter the window portion, thereby making it possible to realize the thinning of the disk drive as a whole. Note that the stator is fixed to the base plate in such a state that an annular main body portion and distal end portions of tees of a stator core are brought into abutment with circumferential edge portions of the window portions.
However, the conventional techniques have had the following problems.
(1) In the conventional general disk drives, since the turntable is made by drawing or cutting a sheet metal, there have been caused problems that the weight of the turntable so made is increased, and when the thickness of the turntable is attempted to be reduced with a view to reducing the weight and thickness thereof, the strength of the turntable is decreased, and that a complex and trouble some working is required for a center portion thereof where a spindle is to be fixed.
(2) In addition, since it is a general practice to form the turntable into a flat shape by drawing or cutting a sheet metal, there has been caused a problem that an unnecessary space is produced between a lower surface of the turntable and the bearing portion and the bearing holding portion, and hence the overall thickness of the disk drive becomes thick, making it difficult to make the disk drive thinner.
(3) Since the hook portions 116 is made up of a separate member from the turntable 109, there have been caused problems that the number of component is increased and that the number of manufacturing manhours required for a press bonding or welding process of fixing the hook portion 16 to the lower surface of the turntable 109 is increased, and additionally, since when attempting to thin the disk drive 100, a vertical length of the hook portion 116 is reduced, there has been caused a problem that a sufficient flexibility cannot be imparted to the hook portion 116, thereby making it difficult to mount the hook portion on the turntable 109.
(4) Since the disk holding claw 113 is not only pushed to a center side of the disk holding portion 112 but also slides downwards when the disk D is installed, there has been caused a problem that the predetermined gap 118 becomes necessary on the upper surface side of the turntable 119 for allowing the disk holding claw 113 to slide downwards, this increasing the overall thickness of the disk drive.
(5) In addition, since a punched sheet metal is used as the base portion 101, there have been caused problems that not only the thickness but also the weight of the disk drive is increased, thereby making it difficult to reduce the weight and thickness of the disk drive and that when attempting to reduce the thickness, the mechanical strength thereof is reduced.
In particular, since a large magnitude of external force is exerted on the base portion 101 via the spindle 108 and the bearing portion 103 when the disk D is installed and removed, a predetermined strength is required. Note that as with the spindle motor in (Patent Document No. 2), while in the event that the distal end portions of the tees of the stator core are brought into abutment with the base plate, a predetermined strength can be obtained, since the stator core and the base plate are made to abut with each other, there has been caused a problem that a magnetic circuit made up of the stator core and the magnet becomes unstable, the efficiency being thereby deteriorated.
(6) Since the circuit board 106 is normally disposed at a lower portion of the stator 105, a large gap needs to be provided between the stator 105 and the base portion 101, there has been caused a problem that a height from a mounting surface (the upper surface of the base portion 101) via which the disk drive is mounted in a housing which constitutes a place where the disk drive is to be mounted and the upper surface of the disk holding portion 112 is increased, thereby making it impossible to realize the thinning of the disk drive.
(7) Since the disk drive 100 needs to be mounted on the housing via a spacer, there has been caused a problem that the number of components is increased, and since dimensional errors are accumulated, there has been caused a problem that the mounting tolerance is increased.
(8) Since there is provided the annular magnet 117 which generates the magnetic attraction force which attracts the turntable 109, a rotating magnetic force is generated relatively by virtue of the rotation of the turntable 109, and the gap between the lower surface of the turntable 109 and the annular magnet 117 differs depending upon positions due to assembling errors or the like, whereby a variation in gap is generated by virtue of the rotation of the turntable 109, a problem being thereby caused that a magnetic loss is generated to thereby deteriorate the efficiency and increase the noise.
(9) In addition, since the annular magnet 117 is provided on the upper surface of the stator core 105a, a space becomes necessary between the turntable 109 and the stator 105 for accommodating the annular magnet 117, a problem being thereby caused that the thinning of the disk drive cannot be realized.
(10) There is caused the state in which the disk holding claw 113 is tilted about the fulcrum 112b after the disk D has been installed due to the effect of the predetermined gap 118 provided between the lower portion of the disk holding claw 113 and the upper surface of the turntable 109, whereby the upper surface 113c of the disk holding claw 113 protrudes further upwards than the upper surface 112c of the disk holding portion 112, and even in the event that the gradient surface 113d is provided with a view to rectifying the protruding state, a height-ways space becomes necessary for the gradient surface 113d so provided, a problem being thereby caused that the thinning of the disk drive is difficult to be realized.
(11) When the thinning of the disk drive proceeds, mechanical dimensions and accuracy inside the disk drive need to be exacting, and as a result, the frequency with which the disk drive is disassembled for rectification is estimated to be increasing. However, as this actually occurs, since the hook portions 116 are provided on the lower surface of the turntable 109, a direct pressing force cannot be applied to the hook portions 116, a problem being thereby caused that the disassembling for rectification becomes difficult once the disk drive has been assembled.
(12) Since the base portion 101 is strongly fixed to the bearing holding portion 102 by plastically deforming the annular portions provided on the lower side of the bearing holding portion 102 through pressing, it becomes difficult to secure a vertical accuracy of the bearing portion 103 based on the mounting surface provided on the base portion 101 via which the disk drive is mounted in the housing due to the effect of the warping of the base portion 101, and additionally, dispersion in height based on the mounting surface tends to be generated easily, a problem being thereby provided that the thinning of the disk drive is difficult to be realized.